1. Field of the Invention
The present invention relates to liquid crystal display devices and apparatus and methods of manufacturing the same, including orientating the alignment layer, dispensing liquid crystal and sealant, bonding, cutting, correcting dispensing errors, and inspecting the completed device.
2. Discussion of the Related Art
As the information age advances, the demand for various display devices has increased. To meet this demand, research regarding flat panel display devices is ongoing including liquid crystal display devices (LCD), plasma display panels (PDP), electro-luminescent displays (ELD), vacuum fluorescent displays (VFD), and the like. Some flat panel display devices are being applied to various appliances for display purposes.
In particular, the LCD has been used as a substitute for the cathode ray tube (CRT) in association with mobile image display devices because the LCD has the advantages of superior picture quality, lightness, thinness, and low power consumption. Thus, the LCD is currently most widely used. The LCD device is a device that displays information on a screen using refractivity anisotropy. Thus, various applications for LCDs are being developed in addition to mobile image display devices such as monitors of notebook computers, but also TV monitors to receive and display broadcast signals and desktop computer monitors.
Although the LCD has been developed so that it can be used as picture display devices in various fields, the task to enhance the quality of images in such LCDs is made difficult by attempting to improve the above-mentioned features and advantages.
Accordingly, successful application of such LCDs to diverse image display devices depends on whether or not the LCD can realize desired high picture quality including high resolution, high brightness, large display area, and the like, while maintaining the desired characteristics of lightness, thinness, and low power consumption.
The LCD device includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the substrates, wherein the lower substrate is formed opposite the upper substrate at a predetermined interval. Alignment of the liquid crystal layer depends on whether a voltage is applied between the two substrates, and transmittance of light depends on the alignment of the liquid crystal layer, whereby an image is displayed. At this time, if the alignment of the liquid crystal layer is disordered, it is difficult to obtain a desired image. Accordingly, an alignment layer is formed to uniformly maintain an initial alignment of the liquid crystal layer.
With reference to FIG. 1, the liquid crystal display panel 10010 includes an image display part 10013 in which liquid crystal cells are arranged in a matrix form, a gate pad part 10014 connected with gate lines 10016 of the image display part 10013 and a data pad part 10015 connected with data lines 10017.
The gate pad part 10014 and the data pad part 10015 are formed at an edge region of a thin film transistor (TFT) array substrate which does not overlap with a color filter substrate 1002. The gate pad part 10014 supplies scan signals provided from a gate driver (not illustrated) to the gate lines 10016 of the image display part 10013, and the data pad part 10015 supplies image information provided from a data driver (not illustrated) to the data lines 10017 of the image display part 10013.
Although not illustrated, the color filter substrate 1002 includes a color filter including red, green and blue sub-color filters implementing colors, a black matrix for separating the sub-color filters and blocking light from transmitting through a liquid crystal layer, and a transparent common electrode for applying a voltage to the liquid crystal layer.
The array substrate 1001 includes a plurality of gate lines 10016 and a plurality of data lines 10017 arranged vertically and horizontally thereon and defining a plurality of pixel regions, the TFT, namely, a switching element, formed at each crossing of the gate lines 10016 and the data lines 10017, and a pixel electrode formed on each pixel region.
The array substrate 1001 and the color filter substrate 1002 are attached in a facing manner by a seal pattern 10040 formed at an edge of the image display part 10013 to form a liquid crystal display panel 10010, and attachment of the two substrates 1001 and 1002 is made through an attachment key (not illustrated) formed on the array substrate 1001 or the color filter substrate 1002.
In order to seek improvement of a yield, in the LCD device, the TFT array substrates are formed on a large-scale mother substrate, color filter substrates are formed on another separate mother substrate, which are then attached to simultaneously form the plurality of liquid crystal display panels. In this case, for the attached mother substrates, a cutting process is required to cut the attached mother substrates into a plurality of unit liquid crystal display panels.
In general, cutting of the mother substrates is performed such that a prearranged cut groove is formed on the mother substrates with a wheel with high hardness compared with glass and then cracking is made along the prearranged cutting groove.
FIG. 2 is a view illustrating the structure of a section of the unit liquid crystal display panel formed by attaching the first mother substrate on which the TFT array substrates are formed and the second mother substrate on which the color filter substrates are formed.
As illustrated, in the unit liquid crystal panels, the thin film transistor array substrates 1001 are protruded at one side compared to the color filter substrates 1002, because the gate pad part (not illustrated) and the data pad part (not illustrated) are formed at the edge portion of the thin film transistor array substrate 1001 which is not overlapped with the color filter substrate 1002.
Accordingly, the color filter substrates 1002 formed on the second mother substrate 10030 are formed to be separated as long as a first dummy region 10031 corresponding to the protruded portion of the thin film transistor array substrates 1001 formed on the first mother substrate 10020.
The unit liquid crystal panels are suitably disposed such that the first and the second mother substrates 10020 and 10030 can be utilized to their maximum, and though they differ depending on a model, the unit liquid crystal panels are usually formed to be separated along a second dummy region 10032.
After the first mother substrate 10020 with the thin film transistor array substrates 1001 formed thereon and the second mother substrate 10030 with the color filter substrates 1002 formed thereon are attached, the liquid crystal panels are cut. At this time, the first dummy region 10031 formed at the portion where the color filter substrates 1002 of the second mother substrate 10030 are separated and the second dummy region 10032 separating the unit liquid crystal panels are simultaneously removed.
Manufacturing an LCD device typically involves providing a first and second substrate having thin-film transistors, drive circuits, color filters and other electrical and optical features formed thereon. Then, an alignment film or alignment layer is provided on one of the two substrates, and the alignment layer is rubbed to achieve a surface texture that will impose an orientation on the liquid crystal. Liquid crystal and sealant are then deposited on the substrates in a manner discussed in detail below, after which the substrates are bonded together. After bonding, the bonded substrates are cut in to panels, the edges are smoothed through grinding or other technique, and the panels are inspected for quality. The details of the panels and the methods employed in their manufacture will be discussed in greater detail herein.
FIG. 3 is a cross-sectional view illustrating a related art liquid crystal display device, and FIG. 4 is a flow diagram illustrating a related art method for manufacturing a liquid crystal display device.
A related art LCD device denoted by reference numeral 1011 includes an upper substrate 1013, a lower substrate 1015, and a liquid crystal layer 1017 between the upper and lower substrates 1013 and 1015, as illustrated in FIG. 3.
The lower substrate 1015 is a substrate having an array of driving components formed thereon. Although not illustrated in FIG. 3, the lower substrate 1015 has a plurality of pixels formed thereon, each of which is formed with a driving component such as a thin film transistor. The upper substrate 1013 is a substrate for color filters, and has color filter layers for realizing actual color formed therein. In addition, each of the upper and lower substrates 1013 and 1015 is formed with a pixel electrode and a common electrode, and coated with an orientation film for orientation of liquid crystal molecules in the liquid crystal layer 1017.
The upper and lower substrates 1013 and 1015 are attached by means of a sealing material 1019. The liquid crystal layer 1017 is disposed between the upper and lower substrates 1013 and 1015 such that an amount of light transmitting through the liquid crystal layer is controlled by driving the liquid crystal molecules using the driving components arranged on the lower substrate 1015, displaying information.
The method for manufacturing the liquid crystal display device generally comprises a driving component array process (also known as a driving device array process) to form the driving components on the lower substrate 1015, a color filter process for forming the color filters on the upper substrate 1013, and a cell process. The method for manufacturing the liquid crystal display device will be described in detail with reference to FIG. 4.
First, in the driving component array process, a plurality of gate lines and data lines are arranged to define pixel regions on the lower substrate 1015, and each of the pixel regions is then formed with a thin film transistor, which is a driving component connected to the gate lines and the data lines (S101). In addition, a pixel electrode is also formed to connect with the thin film transistor by the driving component array process, such that, when a signal is applied to the pixel electrode via the thin film transistor, the pixel electrode drives the liquid crystal layer.
Subsequently, a common electrode, and color filter layers of R, G and B for exhibiting colors are formed on the upper substrate 1013 by the color filter process (S104).
After applying orientation films to the upper and lower substrates 1013 and 1015, the orientation films are rubbed to supply an orientation regulating force or surface securing force (that is, a pre-tilt angle and orientation) to the liquid crystal molecules in the liquid crystal layer formed between the upper and lower substrates 1013 and 1015 (S102, S105).
Next, after spacers for maintaining a constant cell gap are scattered on the lower substrate 1015, and a sealing material 1019 is applied to an outer periphery of the upper substrate 1013, the upper and lower substrates 1013 and 1015 are attached to each other by pressing them together (S103, S106, S107).
Each of the upper and lower substrates 1013 and 1015 is generally formed of a large size glass substrate. As a result, with the color filter layers and the TFT as the driving component formed in each panel region, a plurality of panel regions are formed on a single large size glass substrate. Thus, it is necessary to cut and process the glass substrate (S108). Thereafter, a liquid crystal is injected through a liquid crystal injection hole into each liquid crystal panel processed in the aforementioned manner to form the liquid crystal layer. After the liquid crystal layer is formed by injecting liquid crystals into each processed liquid crystal display panel through a liquid crystal injection port and the liquid crystal injection port is encapsulated, plugged, or sealed, and each liquid crystal display panel is tested and inspected (S109, S110), thus completing manufacturing of the LCD panels.
Inspection of the liquid crystal display panels can be typically divided into appearance inspection, electrical lighting inspection, and orientation abnormality inspection.
The lighting inspection is performed in such a way as to determine whether various electrical components are operating normally by applying a signal to a completed liquid crystal display panel, verifying the results. The appearance inspection is performed in such a way as to determine whether the liquid crystal display panel has an imperfection by inspecting the liquid crystal display panel with naked eyes of an operator. In addition, the orientation abnormality inspection is performed in such a way as to determine whether liquid crystals are gathering or pooling in a lower portion of the liquid crystal display panel that is sagging under its own weight due.
The orientation abnormality of liquid crystals is caused by an undesired increase in volume of the liquid crystal layer resulting from the temperature of the liquid crystal layer within the liquid crystal display panel being too high when manufacturing the liquid crystal display panel. This causes the cell gap of the liquid crystal display panel to exceed the height afforded by the spacer. Accordingly, liquid crystals move to the lower portion of the liquid crystal display panel as it sags, making the cell gap become non-uniform, and thereby deteriorating the quality of the liquid crystal display device.
The orientation abnormality inspection is typically performed by observing an image at the lower portion of the liquid crystal display panel with the naked eyes of the operator while light is transmitted through the liquid crystal display panel. That is, if any abnormality is detected in the image during an observation of the lower portion of the liquid crystal display panel, it is determined that there is orientation abnormality in the liquid crystal display panel.
That is, the orientation abnormality inspection is performed in a state in which the completed liquid crystal display panel is maintained at high temperatures. To this end, the orientation abnormality inspection is performed after each liquid crystal display panel is heated in a heating chamber. Heating of the liquid crystal display panels is typically performed in cassettes for inspection efficiency. In other words, after a plurality of liquid crystal display panels are received in a cassette, they are heated to a high temperature in a heating chamber. The heated liquid crystal display panels are conveyed to an inspection apparatus by means of an additional conveying means, and then subjected to the inspection.
However, such a related art inspecting apparatus for detecting orientation abnormality of the LCD panels has a problem in that, because the inspection apparatus is located a predetermined distance away from the heating chamber, the liquid crystal display panels are exposed to surrounding air and are cooled during conveyance to the inspection apparatus after being transferred from the cassette of the heating chamber, thereby making it impossible to perform a precise inspection.
In addition, the related art orientation abnormality inspecting apparatus has a problem in that, because the interior of the heating chamber is exposed to surrounding air while the liquid crystal display panels are transferred from the cassette of the heating chamber, the surrounding air is induced into the heating chamber, causing a non-uniform temperature of the heating chamber.
Furthermore, because the related art orientation abnormality inspecting apparatus requires expensive mechanisms, including a robot for conveying the liquid crystal display panels from the heating chamber to the inspector, manufacturing costs are invariably increased, and a lot of time is required to convey the liquid crystal display panels.
The Alignment Layer in the Related Art
FIG. 5 is an exploded perspective view illustrating the structure of a LCD device.
As illustrated in FIG. 5, the LCD device includes a color filter substrate 1025, namely, a first substrate, an array substrate 10210, namely, a second substrate, and a liquid crystal layer 10240 formed between the color filter substrate 1025 and the array substrate 10210.
The color filter substrate 1025 includes a color filter (C) comprising sub-color filters 1027 for implementing red (R), green (G) and blue (B) color, a black matrix 1026 for discriminating the sub-color filters 1027 and blocking light transmitting through the liquid crystal layer 10240, and a transparent common electrode 1028 for applying a voltage to the liquid crystal layer 10240.
The array substrate 10210 includes gate lines 10216 and data lines 10217 that are arranged on the substrate 10210 and define pixel regions (P). A thin film transistor (TFT) switching element is formed at respective crossings of the gate lines 10216 and the data lines 10217, and a pixel electrode 10218 is formed at each pixel region (P).
The pixel region (P) is a sub-pixel corresponding to one sub-color filter 1027 of the color filter substrate 1025, and a color image is obtained by combining the red, green and blue types of sub-color filters 1027. Namely, the three red, green and blue sub-pixels form one pixel, and TFTs are connected to the blue, green and blue sub-pixels.
Because the LCD device is a transmissive type display device for displaying images by adjusting an amount of light transmitted through a liquid crystal layer according to an alignment direction of liquid crystal molecules, an alignment process must be performed for the LCD device to provide each liquid crystal molecule with a uniform direction.
When the orientation of the liquid crystal layer is not uniform, it is difficult to obtain the desired image. Accordingly, an orientation or alignment film for uniformly maintaining initial orientation state of the liquid crystal layer is formed on the upper and lower substrates. An alignment film (not illustrated) for aligning liquid crystal molecules of the liquid crystal layer 10240 is formed on the color filter substrate 1025 and the array substrate 10210.
In general, many methods are known to produce an alignment layer. The orientation direction of the orientation film may be established using a rubbing alignment method or a light irradiating method, also known as a photo-alignment method. An alignment method using a rubbing operation is currently used most frequently. The rubbing alignment method first forms an alignment layer on a substrate and then rubs the alignment layer by use of a rubbing cloth to form uniform microgrooves on a surface of the alignment layer. The alignment layer having the microgrooves on its surface provides each liquid crystal molecule with an alignment controlling force, thereby constantly aligning the liquid crystal molecules over the entire surface of the alignment layer in a desired direction.
In the rubbing method, a thin orientation film is deposited on a substrate, and a rubbing roll onto which a rubbing cloth is wound is rolled on the orientation film, thereby orienting the orientation film in a designated direction.
In the light irradiating method, a thin orientation film is deposited on a substrate, and ultraviolet rays, such as polarized rays or non-polarized rays, are irradiated onto the orientation film. A reaction resulting from the irradiation orients the orientation film in a designated direction.
When using either the rubbing or the light irradiating method, a thin orientation film or alignment layer having a small thickness is uniformly deposited on a substrate. A related art roll printing method is used to deposit the orientation film.
FIG. 6 illustrates a method for forming or coating an alignment film using a related art roll printing method and device.
As illustrated, generally, an alignment film is formed using a printing method using a plurality of rolls. Namely, an alignment solution 10224 supplied between a cylindrical anilox roll 10222 and a cylindrical doctor roll 10223 is uniformly coated entirely on the anilox roll 10222 as the anilox roll 10222 and the doctor roll 10223 are rotated. In this case, the alignment solution 10224 is supplied by a dispenser 1021 in an injector type.
The anilox roll 10222 is rotated in contact with a printing roll 10224 having a rubber plate or printing mask 10225 attached on a certain region of its surface, thereby transferring the alignment solution 10229 on the anilox roll 10222 to the rubber plate 10225. The rubber plate 10225 corresponds to a substrate 10226 on which the alignment solution or orientation material 10229 is to be coated, and has a master pattern to allow the alignment film to be selectively printed on the substrate 10226.
As a printing table or substrate stage 10227 with the substrate 10226 loaded thereon is moved in contact with the printing roll 10224, the alignment solution 10229 which has been transferred to the rubber plate 10225 is re-transferred onto the substrate 10226 to thereby form an alignment film.
Next, with the alignment film formed on the substrate, the alignment film is rubbed to arrange or orient liquid crystals in a certain direction to form valleys in a certain direction.
The related art roll printing method for realizing uniform coating of the alignment material using the doctor roll 10223 has several problems
First, as the size of the substrate increases, the size of the anilox roll 10222 increases along with the size of the doctor roll 10223 rotating in engagement with the anilox roll 10222. In this case, a problem occurs in that the alignment material is not uniformly coated on a center portion of the anilox roll 10222.
Referring to FIG. 8, if the sizes of the doctor roll 10316 and the anilox roll 10318 increase, pressure between the doctor roll 10316 and the anilox roll 10318 decreases in a center portion (portion B) of the rolls 10316 and 10318 more seriously than the pressure between the end portions (portions A) of the rolls 10316 and 10318. Accordingly, the alignment material is not uniformly coated on the center portion (portion B) of the anilox roll 10318.
Second, if coating is repeated, a predetermined portion of the doctor roll 10223 is abraded. In this case, the alignment material is not uniformly coated on the abraded portion. For this reason, a problem occurs in that a spot is generated on a predetermined portion of the substrate.
In other words, since the doctor roll 10223 is made of a rubber based material, it is abraded by the alignment material if coating is repeated, whereby the alignment material is not uniformly coated on the doctor roll 10223.
In addition, the roll printing unit is fixed and the substrate stage 10227 moves, thus allowing the orientation material 10229 to be deposited on the substrate 10226.
FIG. 7 is a perspective view illustrating a rubbing process.
As illustrated, the alignment film 10221 is rubbed to form recesses 10236 on the surface thereof. The rubbing process rubs the surface of the alignment film 10221 in a certain direction using a roller 10230 with a rubbing cloth 10235 wound thereon.
After the surface of the alignment film 10221 is rubbed, it has fine recesses 10236.
For the rubbing cloth 10235, a soft cloth is used. The rubbing equipment, including the roller 10230, is relatively simple. The basic part for setting conditions for the rubbing process is setting a rubbing condition with a suitable strength and applying a uniform rubbing strength on a large area.
There are problems that arise in the related art rubbing process. The rubbing process may include a rubbing cloth that is wound on a rubbing roll and then is placed in contact with the rubbing roll while the rubbing roll is rotated and moved in one direction. Meanwhile, the LCD device is being employed in electric devices such as TV sets as well as portable electric devices recently and accordingly, the size of the LCD device is greatly increasing (furthermore, the mother substrate for fabricating LCD panels is much greater in size) that results in an increase of the width and weight of the rubbing roll used to perform the alignment process for a large LCD device.
In the meantime, the alignment controlling force or a surface fixing force of the alignment layer that is rubbed by the rubbing roll is determined by the microgrooves formed in the alignment layer, and the depth of the microgroove is different based upon a pressure of the rubbing roll applied to the alignment layer. However, as the width and weight of the rubbing roll increases, it is difficult to uniformly maintain the pressure applied to the mother substrate, that results in the fabrication of a defective LCD device by defectively rubbing the alignment layer.
If the rubbing is not uniformly performed, an alignment degree of liquid crystal molecules is not spatially uniform, causing a defect that optical characteristics are different at a certain portion.
And because the physical units such as the rolls are used in the rubbing process, management of the rolls is important with respect to stability of processes. Accordingly, it is important to secure a sufficient number of rubbing rolls to obtain a margin in operating rolls. However, there is no means for keeping and storing the rubbing rolls, and the rubbing rolls are kept standing vertically, limiting the operation of rolls. In addition, as the size of the mother substrate for fabricating a liquid crystal display panel increases, the corresponding rubbing roll lengthens, so there is a limitation on keeping rubbing rolls in a standing state in a clean room having a limited amount of space.
Furthermore, since the rubbing rolls are kept in a fixed state, the eccentricity of the rubbing roll deviates and changes. The eccentricity of the rubbing roll is a critical factor for coordinating and managing a rubbing process along with the condition of a rubbing cloth.
Moreover, since the rubbing rolls are kept in an open, exposed state, the rubbing cloth is inevitably contaminated by external particles, thereby causing damage to the surface of the liquid crystal display panel.
With respect to FIG. 6, when forming an orientation layer on a large sized substrate, the movement of the substrate stage unit 10227 during forming the orientation layer is increased, thereby increasing the space occupied by the roll printing device, and lowering space utilization.
Providing Liquid Crystal in the Related Art
Related art methods of dropping or dispensing liquid crystal are described as follows. As illustrated in FIG. 9, the conventional liquid crystal display device comprises a lower substrate 1041 and an upper substrate 1043, which are opposite to each other. Although not illustrated in the drawings, TFTs and pixel electrodes are formed on the lower substrate 1041, and a light shielding film, color filter layers, and common electrodes are formed on the upper substrate 1043.
A liquid crystal layer 1045 is formed between the lower substrate 1041 and the upper substrate 1043. The liquid crystal layer 1045 is oriented in a designated direction by an orientation film (not illustrated) formed on the lower surface thereof.
A sealant layer 1047 is formed between the lower substrate 1041 and the upper substrate 1043. The sealant layer 1047 serves to seal the liquid crystal layer 1045 and to bond the lower substrate 1041 and the upper substrate 1043 to each other.
By way of another example, FIG. 10 illustrates an exploded perspective view of an LCD device according to the related art.
As illustrated in FIG. 10, an LCD device according to the related art includes a lower substrate 10510, an upper substrate 10520, and a liquid crystal layer (not illustrated) formed between the lower and upper substrates 10510 and 10520.
The lower substrate 10510 includes gate and data lines 10512 and 10514 crossing each other to define a unit pixel region. Then, a thin film transistor TFT is formed adjacent to a crossing portion of the gate and data lines 10512 and 10514, wherein the thin film transistors TFT functions as a switch. Also, a pixel electrode 10516 is formed in the pixel region, wherein the pixel electrode 10516 is connected with the thin film transistor TFT.
The upper substrate 10520 includes a black matrix layer 10522 for preventing light leakage from other portions except the pixel region, a color filter layer 10524 of red, green and blue patterns for representing colors in the portion corresponding to the pixel region, and a common electrode 10526 formed on the color filter layer 10524.
The above-configured liquid crystal display device is fabricated by preparing the lower and upper substrates and forming a liquid crystal layer between the prepared substrates. In this case, the liquid crystal layer is formed between both of the substrate by a vacuum injection method or a liquid crystal dropping method.
The vacuum injection method is carried out by forming a sealant having one inlet on one of the two prepared substrates, bonding the two substrates together and injecting liquid crystals into a space between the two substrates via the inlet.
By way of example, the injecting of the liquid crystal may be achieved by the following processes. That is, as illustrated in FIG. 11, a nitrogen gas (N2 gas) is supplied into a vacuum chamber in a state where an injection hole 10616 of a liquid crystal panel 1061 is in contact with the liquid crystal, and thus a degree of vacuum of the chamber 10610 is lowered. Then, the liquid crystal 10614 is injected into the panel 1061 by the difference between the internal pressure of the liquid crystal panel 1061 and the pressure of the vacuum chamber 10610. After the panel 1061 is completely filled with the liquid crystal, the injection hole 10616 is encapsulated by an encapsulating material, thereby forming a liquid crystal layer (This type of injection method is called a vacuum injection method of liquid crystal).
However, disadvantageously, it takes a long time to inject liquid crystal into a panel through the injection hole 16. That is, only a very small amount of liquid crystal is injected into the liquid crystal panel per unit time because this is only a very small gap of just a few micrometers (μm) between the driving device array substrate and the color filter substrate of the liquid crystal panel. For example, when a liquid crystal panel of approximately 15 inches is fabricated, it takes approximately 8 hours to complete the injection of liquid crystal. Such injection of liquid crystal over a long period of time delays the fabrication process of the liquid crystal panel, and thus deteriorates fabrication efficiency. Particularly, the vacuum injection method is inadequate for a large-sized liquid crystal panel because the time it takes to inject liquid crystal increases as liquid crystal panels become larger.
As a size of a substrate increases, it takes so much time in injecting liquid crystals by the vacuum injection method as to reduce manufacturing productivity. In addition, because the sealant layer is hardened under the condition that the liquid crystal layer is formed between the lower and upper substrates, the liquid crystal drop method causes domain defects due to a scattering of the orientation of the liquid crystal layer from high temperatures during hardening the sealant layer.
That is, in the liquid injection method, since the liquid crystal is injected into a space between the lower and upper substrates after the sealant layer is hardened, the liquid crystal layer is not exposed to high temperatures generated during hardening the sealant layer. However, in the liquid drop method, since the sealant layer is hardened after the liquid crystal layer is formed between the lower and upper substrates, the liquid crystal layer is exposed to high temperatures generated during hardening the sealant layer, and thus the orientation of the liquid crystal layer is scattered.
Thus, the liquid crystal dropping method is more suitable for large-scale substrates. The liquid crystal dropping method is carried out by forming a sealant having no inlet on one of the two prepared substrates, dropping liquid crystals on the substrate and bonding the two substrates together. However, in the liquid crystal dropping method it is difficult to calculating the proper quantity of liquid crystals.
In particular, the liquid crystal dropping method differs from the vacuum injection method in dropping a prescribed quantity of liquid crystals after calculating a liquid crystal quantity by considering a cell size, a cell height and the like. It is substantially difficult to calculate a precise quantity of liquid crystals due to various factors.
If the liquid crystal quantity calculated is too small, a filling-failure area of liquid crystals is generated within a liquid crystal display panel. If the liquid crystal quantity calculated too large, an over-filling area is generated within a liquid crystal display panel, lowering the quality of the display.
Many efforts have been made to minimize the generation of the insufficient or excessive filling of liquid crystals in various ways. Once the insufficient or excessive filling of liquid crystals takes place, there is no way in the related art to correct the insufficient or excessive filling of liquid crystals. If the filling error is serious, the corresponding panel must be discarded, which is not economical.
Providing Sealant in the Related Art
In the liquid crystal injection method, a sealant is dispensed in a pattern having an inlet on any one of lower and upper substrates, and the lower and upper substrates are bonded to each other. Then, liquid crystal is injected to a space between the lower and upper substrates through the inlet of the sealant.
In the liquid crystal dispensing method, a sealant is dispensed in a pattern having no inlet on the lower substrate, and liquid crystal is dispensed on the lower substrate. Then, the lower and upper substrates are bonded to each other.
The method for dispensing the sealant of the pattern having no inlet by the liquid crystal dispensing method is classified into a screen printing method and a dispensing method using a dispenser. If applying the screen printing method, the screen may come into contact with a substrate, whereby it may damage an alignment layer of the substrate. In this respect, the dispensing method is used generally.
Hereinafter, a related art dispensing method will be explained with reference to the accompanying drawings.
FIG. 12 is a schematic view of a sealant dispensing method using a dispenser according to the related art.
First, as illustrated in FIG. 12, the related art dispenser is provided with a syringe 10710 and a nozzle 10720.
The syringe 10710 has a sealant 10715 therein. The nozzle 10720 is connected to a lower end of the syringe 10710 to supply the sealant 10715 to a substrate 1071.
The dispenser moves along a direction (as indicated by the arrow in the figure) from a starting point (s) of the substrate 1071, and then returns to the starting point (s) of the substrate 1071, forming a closed sealant path. As the dispenser moves along the substrate, the sealant 10715 is discharged to the substrate 1071 through the nozzle 10720. Accordingly, the sealant 10715 of the pattern having no inlet is dispensed to the substrate 1071.
However, the related art sealant dispensing method has the following disadvantages.
First, because the sealant 10715 has a particular viscosity, the sealant 10715 may coagulate in the end of the nozzle 10720 of the dispenser. Thereafter, when the sealant material is supplied to the starting point (s) of the substrate 1071 through the nozzle 10730, the coagulated sealant is discharged to the starting point (s) of the substrate 1071. In addition, because the dispenser moves along the arrow direction from the starting point (s) of the substrate 1071, and then turns back to the starting point (s) of the substrate 1071, the coagulated sealant 10715 may be excessively dispensed to the starting point (s) of the substrate 1071. In this case, when bonding the two substrates to each other, the sealant 10715 spreads to the inside of the substrate 1071 in which the liquid crystal is formed. Thus, the liquid crystal dispensed on the substrate 1071 may be contaminated due to the spread of sealant.
Second, to prevent the sealant 10715 from being coagulated at the starting point (s), the dispenser may be stopped before the starting point (s). In this case, the sealant 10715 can be disconnected. That is, the liquid crystal flows to the outside through the disconnected portion of the sealant.
Another example of a related art dispensing device is illustrated in FIG. 13. FIG. 13 is a schematic view illustrating a sealant forming method using a dispenser according to the related art.
The dispenser is provided with a syringe 10810, a nozzle 10820, and a dispensing tube 10830. The syringe 10810 has a sealant 10815 therein. The nozzle 10820 is connected to a lower end of the syringe 10810 to supply the sealant 10815 to a substrate 1081. The dispensing tube 10830 is connected to an upper end of the syringe 10810 to discharge the sealant 10815 through the nozzle 10820 by applying a pressure to the syringe 10810.
A sealant forming method using the above dispenser will now be explained.
The dispenser moves along an arrow direction from a starting point(s) of the substrate 1081, and then turns back to the starting point(s) of the substrate 1081. During the movement of the dispenser, a predetermined pressure is applied to the syringe 10810 through the dispensing tube 10830 so that the sealant 10815 is discharged to the substrate 1081 through the nozzle 10820. Accordingly, the sealant 10815 is dispensed to the substrate 1081.
After completion of dispensing the sealant 10815, the dispensing tube 10830 is closed to stop the discharge of the sealant 10815. Thereafter, the dispenser is moved to a predetermined position and dispenses another sealant material according to the above-mentioned method to form a plurality of sealant patterns on the substrate 1081.
However, the dispenser and sealant dispensing method according to the related art has the following disadvantages.
After completion of dispensing one sealant material, the dispensing tube 10830 is closed to stop the discharge of the sealant 10815 from the nozzle 10820. At this time, the sealant may coagulate in the nozzle 10820. Thereafter, when another sealant material is supplied to the substrate 1081 through the nozzle 10820, the coagulated sealant is discharged to the starting point of the substrate 1081, thereby making it difficult to uniformly dispense sealant materials. Because of this problem, it has been necessary to start dispensing the sealant in a dummy region away from the panel area. This way any dried or coagulated sealant is dispensed away from the panel's sealant area. Sealant dispensing patterns include ribbon patterns or other starting paths in the dummy region. The problem with these solutions is that they require the dispensing of sealant across the scribing or cutting path on the substrate. Scribing or cutting through the hardened sealant can damage or wear out the scribing or cutting tool.
Fabrication in the Related Art
A related art LCD device denoted by reference numeral 1011 includes an upper substrate 1013, a lower substrate 1015, and a liquid crystal layer 1017 between the upper and lower substrates 1013 and 1015, as illustrated in FIG. 3.
The lower substrate 1015 is a substrate having an array of driving components formed thereon. Although not illustrated in FIG. 3, the lower substrate 1015 has a plurality of pixels formed thereon, each of which is formed with a driving component such as a thin film transistor. The upper substrate 1013 is a substrate for color filters, and has color filter layers for realizing actual color formed therein. In addition, each of the upper and lower substrates 1013 and 1015 is formed with a pixel electrode and a common electrode, and coated with an orientation film for orientation of liquid crystal molecules in the liquid crystal layer 1017.
The upper and lower substrates 1013 and 1015 are attached by means of a sealing material 1019. The liquid crystal layer 1017 is disposed between the upper and lower substrates 1013 and 1015 such that an amount of light transmitting through the liquid crystal layer is controlled by driving the liquid crystal molecules using the driving components arranged on the lower substrate 1015, displaying information.
The method for manufacturing the liquid crystal display device generally comprises a driving component array process to form the driving components on the lower substrate 1015, a color filter process for forming the color filters on the upper substrate 1013, and a cell process. The method for manufacturing the liquid crystal display device will be described in detail with reference to FIG. 4.
The steps in FIG. 4 are each performed on respective processing lines. Accordingly, the substrates 1013 and 1015 that have undergone one process are transferred to a subsequent processing line by a conveyor or an auto guide vehicle. However, when an LCD device having a large area is being fabricated, a large substrate has to be transferred in a factory. Since conveyors are not well suited for transferring the large substrate, the auto guide vehicle is mainly used to transfer the large substrate to a processing line.
When using the auto guide vehicle, a plurality of substrates is received in a cassette thereby to be transferred. Unloading the substrate from a processing line, receiving the substrate in a cassette, and loading the received cassette onto a next processing line are performed by a robot.
FIG. 14 illustrates a cassette for an LCD device according to the related art in which substrates are received for transfer by an auto guide vehicle. As illustrated, the cassette 10940 of the related art for receiving an LCD device comprises a main body 10941, a supporting bar 10942 formed in the body to receive a substrate 10910, and a pad 10944 formed at the supporting bar 10942 to fix the substrate 10910 by contacting the substrate 10910. The supporting bars 10942 are formed in the body 10941 as a multiple layers thereby to receive a plurality of liquid crystal panels 1093.
FIG. 15 is a plan view illustrating the interior of the cassette 10940 of FIG. 14 in accordance with the related art, in which the substrate 10910 is received on one layer in the cassette 10940. As illustrated, a plurality of LCD panels 1093 are formed on the substrate 10910, and the LCD panels 1093 are separated from each other with a certain distance by a dummy region. A plurality of supporting bars 10942 for supporting the substrate 10910 are formed in the body 10941 (the same number of supporting bars 10942 are formed at upper and lower portions of the body 10941). That is, the substrate 10910 is received in the cassette 10940 by the plural supporting bars 10942. The supporting bar 10942 is provided with a plurality of pads 10944. The pads 10944 are formed of a material such as rubber able to absorb an impact and having an excellent coefficient of friction for fixing the substrate 10910 and to prevent impact damage to the substrate 10910. The pad 10944 contacts the dummy region 1094 of the substrate 10910.
When the substrate 10910 is received in the cassette 10940, the cassette 10940 is transferred to a next processing line by an auto guide vehicle and then unloaded from the cassette 10940 by a robot or other means thereby to undergo a corresponding process.
However, the cassette of the related for an LCD device has the following problems.
As techniques for fabricating LCD device develop and the number of electronic devices employing LCD devices increases, LCD devices having various sizes are being fabricated. Methods for fabricating LCD devices having various sizes in one fabrication line are widely used. Accordingly, the size of an LCD panel formed on a substrate to be transferred from one processing line to another processing line is not always the same, but varies according to a model of a LCD device being fabricated.
FIG. 16 is a view illustrating a cassette 10940 in which a substrate 10910 has been received on which LCD panels 10930 are formed each having a wider area than that of the LCD panels of FIG. 15. Since the LCD Panels illustrated in FIGS. 15 and 16 have different sizes from each other, a position on the substrate 10910 where the LCD panel 1093 is formed in FIG. 16 is different from a position of the LCD panel 1093 on the substrate 10910 in FIG. 15. A pad 10944 is positioned at a dummy region 1094 of the substrate 10910 in FIG. 15. However, in FIG. 16, the pad 10944 is positioned differently relative to the LCD panels 1093.
When the substrate 10910 is received in the cassette 10940 of FIG. 15, a dummy region of the substrate 10910 contacts the pad 1094. As a result, even when the substrate 10910 pressed, a defect is not generated. However, when the pad 1094 is positioned within the LCD panel 1093 as illustrated in FIG. 16, if the substrate 10910 is pressed, the pad 10944 presses on an area of the LCD panel 1093 for displaying an image and a defect in the LCD device may result. The above problem occurs primarily at the time of transferring attached LCD panels that have been received in the cassette 10940 to another processing line. As the LCD panel 1093 is pressed against a pad, a stain is generated on the LCD device.
As noted earlier, in the liquid crystal dispensing method, one substrate is prepared on which a liquid crystal material has been dispensed. Another substrate is prepared on which a sealant pattern is formed such that the sealant pattern extends completely along the peripheral edge of the substrate without forming an injection port. Thereafter, the latter substrate is arranged on the former substrate under a vacuum condition such that they are aligned with each other. The aligned substrates are then bonded to each other. Such a liquid crystal dispensing method is disclosed in Japanese Patent Application Nos. Heisei 11-089612 and Heisei 11-172903.
For this reason, active research has recently been undertaken to provide various equipment for use in the liquid crystal dispensing method.
For example, the applicant proposed a substrate bonding apparatus for an LCD panel through Korean Patent Application No. 2002-71366 (Filing date: Nov. 16, 2002).
Where it is desired to bond an upper substrate (or a lower substrate) to a lower substrate (or an upper substrate) coated with a sealant along the peripheral edge of the lower substrate and with a liquid crystal material dispensed thereon, using the substrate bonding apparatus proposed by the applicant. The upper substrate is first attached to an upper electrostatic chuck (ESC) and is then lowered such that the upper substrate is near the lower substrate. The upper ESC is then turned off, thereby releasing the upper substrate which is, in turn, laid on the lower substrate. In this state, the substrate bonding apparatus performs a venting process to bond the upper and lower substrates to each other.
An example of the venting process is illustrated in FIG. 17A. As illustrated in FIG. 17A, during the venting process, a vacuum is formed in a space defined between an upper substrate 110110 and a lower substrate 110120, and sealed by a sealant 110111 formed on the lower substrate 110120, thereby generating a pressure difference between the space and the atmosphere. By virtue of the pressure difference, the upper substrate 110110 and lower substrate 110120 are bonded to each other.
However, as illustrated in FIG. 17B, the above-mentioned conventional substrate bonding apparatus has a problem in that venting is non-uniformly carried out in the venting process, thereby causing the bonding quality of the substrates to be poor. That is, when venting is non-uniformly carried out in the venting process, a gap is formed between the upper substrate 110110 and the sealant 110111. In this case, an air bubble may be introduced into the liquid crystal space, thereby causing the bonding quality of the substrates to be poor.
Cutting Substrates in the Related Art
As described above, after the panels are bonded together, they must be cut. The cutting process of the liquid crystal display panel will be described as follows.
FIG. 18 is an exemplary view illustrating a cutting process of the liquid crystal display panel.
As illustrated, a cutting device of the liquid crystal display panel includes a table 11142 on which the first and second mother substrates 11120 and 11130 for which previous processes have been terminated, are loaded, and a cutting wheel 11155 for processing the first and second mother substrates 11120 and 11130 to form prearranged cut lines 11151.
In the cutting device of the liquid crystal display panel, when the first and second mother substrates 11120 and 11130 including a plurality of liquid crystal display panels and attached in a facing manner are loaded on the table 11142, the cutting wheel 11155 positioned at an upper side of the first and second mother substrates 11120 and 11130 is lowered and rotated in a state that certain pressure has been applied to the second mother substrate 11130, to thereby form prearranged cut lines 11151 in a groove form on the surface of the second mother substrate 11130.
The prearranged cut lines are also formed on the first mother substrate 11120. Namely, the first mother substrate 11120 is processed with the cutting wheel 11155 to form prearranged cut lines at the same positions as the prearranged cut lines 11151 of the second mother substrate 11130. Accordingly, in the liquid crystal panel cutting process, since the first and second mother substrates 11120 and 11130 are processed to form the prearranged cut lines 11151, after the second mother substrate 11130 is processed with the cutting wheel 11155, the liquid crystal panel is reversed to make the first mother substrate 11120 to face upward and then the first mother substrate 11120 is processed with the cutting wheel 11155.
Thereafter, pressure is applied to the prearranged cut lines 11151 formed on the first and second mother substrates 11120 and 11130 to separate the first and second mother substrates 11120 and 11130. And then, the first and second mother substrates 11120 and 11130 are separated such that the first and second mother substrates 11120 and 11130 are broken with a breaking bar so that cracking can be made along the prearranged cut lines 11151.
In cutting the liquid crystal display panel, a scribing process and a breaking process are performed several times through a plurality of passes.
Thus, much time is required for the scribing process and the breaking process causing the problem of a reduction in productivity.
In particular, according to the cutting method of the liquid crystal display panel, since the mother substrates are struck with the breaking bar to make cracks along the prearranged cut lines formed on the mother substrates, a plurality of glass chips are generated, and if the striking is not performed inaccurately or if cracking is not incompletely made, the liquid crystal display panel would be damaged or torn off when it is extracted.
Typically, the scribing process is implemented by forming scribing lines by use of a cutting wheel, while the breaking process is implemented by cutting the substrate along the scribing lines by use of a steam-cutting device.
FIG. 19A illustrates a substrate 11240 processed by the cutting wheel and a pressing bar of the related art. As illustrated in FIG. 19A, a scribing line 11232 is formed on the substrate 11240 including a plurality of LCD panels using the cutting wheel. The substrate 11240 is cut along the scribing line 11232 by pressure of the pressing bar.
A related art cutting process for manufacturing the liquid crystal display panel will be described hereinafter with reference to FIG. 3.
FIG. 19B-19I illustrate a cutting process of the liquid crystal display panel of the related art.
As illustrated, a cutting device of the liquid crystal display panel includes a table 911242 on which the bonded first and second mother substrates 911220 and 911230 are loaded, and a cutting wheel 911255 for processing the first and second mother substrates 911220 and 911230 to form prearranged cut lines 911251.
When using the cutting device of the related art, after the bonded first and second mother substrates 911220 and 911230 having a plurality of liquid crystal display panels are loaded on the table 911242, the cutting wheel 911255 positioned at an upper side of the first and second mother substrates 911220 and 911230 is lowered and rotated to apply a certain pressure against the second mother substrate 911230 to form prearranged cut lines 911251 or grooves on the surface of the second mother substrate 911230.
The prearranged cut lines are also formed on the first mother substrate 911220. The first mother substrate 911220 is processed with the cutting wheel 911255 to form prearranged cut lines at the same positions as the prearranged cut lines 911251 of the second mother substrate 911230. Accordingly, in the liquid crystal panel cutting process of the related art, since the first and second mother substrates 911220 and 911230 are to be processed to form corresponding prearranged cut lines, after the second mother substrate 911230 is processed with the cutting wheel 911255, the liquid crystal panel is reversed to have the first mother substrate 911220 face upward and the first mother substrate 911220 is processed with the cutting wheel 911255.
Thereafter, pressure is applied to the prearranged cut lines 911251 formed on the first and second mother substrates 911220 and 911230 to separate the first and second mother substrates 911220 and 911230 along the prearranged cut lines 911251. The first and second mother substrates 911220 and 911230 are separated by striking the first and second mother substrates 911220 and 911230 with a breaking bar to make and propagate a crack along the prearranged cut lines 911251.
In cutting the liquid crystal display panel, a scribing process and a breaking process are performed several times through a plurality of reversals and positionings of the substrates 911220 and 911230. The significant amount of time used for the scribing process and the breaking process reduces productivity of the overall manufacturing process.
In addition since the mother substrates are struck with the breaking bar to make cracks along the prearranged cut lines formed on the mother substrates, a plurality of glass chips are generated. Further, if the striking is performed inaccurately or if crack propagation is incomplete, the liquid crystal display panel may be damaged or torn off when it is extracted.
However, several problems may occur when cutting the substrate using the cutting wheel and the pressing bar as follows.
In order to separate the LCD panel from the substrate that is completely cut by the pressing bar, the cut dummy substrate is lowered below the cut line by gravity. Accordingly, a separate space is required below the cut line. Additionally dust may be generated when the dummy substrate is lowered. Further, if a substrate is not cut into using the pressing bar, the uncut substrate is transferred to later processes resulting in stopping of the later process.
For example, a substrate defect may occur. The cutting method using the cutting wheel involves the application of a mechanical force to a substrate with the cutting wheel. When processing a substrate by pressing the cutting wheel on the mother substrate, the depths of the scribing lines may vary according to a pressure generated between the cutting wheel and the substrate. The varied depths of the scribing lines may result in portions of the substrate not being separated when applying the pressure to separate the unit LCD panels and portions of the substrate may be destroyed or taken away.
Secondly, foreign materials may be generated. When processing the substrate with the cutting wheel, foreign materials such as glass chips may be generated. The generated foreign materials may cause defects in processes in processing lines in a factory.
Examination and Inspection in the Related Art
The LCD panel is typically tested (inspected) by a visual inspection and an electrical lighting test. The lighting test is performed by applying a signal to a completely fabricated LCD panel to detect (test) whether various electric devices are operating normally, while the visual inspection is performed by an operator conducting a naked eye inspection of the LCD panel to determine whether the LCD panel has been defectively fabricated.
A typical apparatus for visually inspecting an LCD panel includes a test board having a lamp therein for outputting light. An LCD panel is transferred to the visual inspection apparatus to be placed on the test board and a polarizer is positioned on the LCD panel. A signal is applied to the LCD panel and the LCD panel is illuminated by light transmitted from the lamp provided in the test board. The operator observes light transmitted through the LCD panel to detect defects in the LCD panel.
FIGS. 20 and 21 illustrate a related art visual inspection apparatus for testing an LCD panel appearance, wherein FIG. 20 is a side sectional view of the visual inspection apparatus and FIG. 21 is a plane view thereof.
As illustrated in FIGS. 20 and 21, a related art apparatus for visually inspecting an LCD panel 11320 includes a test board 11322 including a lamp installed therein for transmitting light to the LCD panel 1131 placed thereon; a camera 11324 positioned at an upper portion of the test board 11322 for capturing alignment marks (not illustrated) formed at an outer periphery of the LCD panel 1131 to thus determine whether the LCD panel 1131 has been aligned on the test board 11322; a jig 11332 disposed at a lower portion of the test board 11322 supporting a polarizer 11330 and having holes 11327; and a plurality of jig pins 11326 formed at the test board 11322 to be inserted into the holes 11327 of the jig 11332 to thus fix the jig 11332 to the test board 11322, thereby fixing the polarizer 11330 onto the LCD panel 1131.
The test board 11322 is inclined by about 60° relative to the ground and has a lamp therein. When an operator puts the LCD panel 1131 on the test board 11322, the camera 11324 captures the alignment marks formed on the LCD panel 1131 to provide information regarding the state of alignment of the LCD panel 1131. With the LCD panel 1131 aligned on the test board 11322, the operator inserts the jig pins 11326 formed at the test board 11322 into the holes 11327 formed in the jig 11332 to position the polarizer 11330 on the LCD panel 1131. With the polarizer fixed, a signal is applied to the LCD panel 1131 and a transmissivity of light transmitted through the LCD panel is changed according to a signal applied to the LCD panel 1131. The operator observes the light transmitted through the polarizer 11330 to evaluate the quality of the LCD panel.
The jig 11332 supports the polarizer 11330. The operator manipulates the jig 11332 rather than the polarizer 11330 to position the polarizer 11330 on the test board 11322. The jig pins 11326 are inserted into the holes 11327 formed in the jig 11332 to fix the jig 11332, and thus the polarizer 11330, onto the test board 11322.
However, the above described visual inspection apparatus for the LCD panel may generate problems as follows.
In order to fix the polarizer 11330 by inserting the jig 11332 into the jig pins 11326, the operator must manually hold the jig 11332 while inserting the jig pins 11326 of the test board 11322 into the holes 11327 of the jig 11332. However, with a the large-sized LCD panel 1131, the corresponding large size of the polarizer 11330 makes it physically difficult or impossible for the operator to manually insert the jig pins 11326 into the holes 11327 of the jig 11332. In addition, while attaching or detaching the polarizer 11330, the polarizer 11330 may strike the camera 11324, resulting in damage to the camera 11324 or to the polarizer 11330.